Gas generator, method for the production thereof and module having a gas generator

ABSTRACT

An inflator as well as a method of manufacturing an inflator, a module including an inflator and an airbag module. In an inflator, especially for a protective device in a vehicle, comprising plural components a sealant is applied in the area of abutting components, especially a sealant which adheres to both abutting components.

FIELD OF THE INVENTION

The invention relates to an inflator, especially for a protective devicein a vehicle, a module equipped with an inflator as well as an airbagmodule. Further, the invention relates to a method of manufacturing aninflator, especially for controlling the tightness of an inflator.

BACKGROUND OF THE INVENTION

Gas generators or inflators for protective devices in a vehicle drivee.g. parts (propping up of hoods, tensioning of the belt, shifting ofcushions or the like) or inflate airbags.

Inflators must be operable for many years for singular use, that is,they may be exposed to high requirements in terms of stability toenvironmental influences such as penetration of moisture or corrosion.

Inflators consist of several interconnected parts. Between abuttingparts a reliable connection lasting for many years is required asprotection against environmental influences from outside.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, an inflator is providedespecially in accordance with the type described above and/orhereinafter in which in the area of abutting parts a sealant is appliedto the parts, especially a sealant adhering to both abutting parts. Saidsealant preferably is an additional agent serving for the tightnesswhich is not the only connecting means between the abutting parts.

The sealant preferably adopts no mechanical or adhesive holding functionbetween the abutting parts which are interconnected otherwise. That isto say, even without a sealant the inflator is designed such that theabutting parts are fixed in position.

As the sealant adheres to both abutting parts, moisture is preventedfrom penetrating the interior of the inflator.

The abutting parts to which the sealant is applied form at least part ofthe outer inflator surface and/or are especially made of differentmaterials. The preferred embodiment provides that one part is made ofplastic material and the other is made of metal. Due to the stronglydifferent expansion coefficients and properties of these parts, theinvention provides an optimized protection against environmentalinfluences.

The part consisting of plastic material especially constitutes a partialinjection-molding around the metallic component. Although suchinjection-molding also ensures a tight, even moisture-tight connectionbetween these parts which, apart from the form closure, also permitsadhesion, the sealant provides additional safety against environmentalinfluences during the service life of an inflator, as it would bepossible at least theoretically that in the course of time small gapsmight occur by virtue of the different thermal expansions and thedifferent expansion behavior.

It is mentioned in this context that inflators and thus the connectionof the parts and the efficiency of the sealant have to reliably operateand act within a temperature range of at least −40° C. to at least 120°C. In order to fulfill these properties, the sealant exhibits highflexibility even with low temperatures. Further properties include lowviscosity in the liquid state during application for penetratingmicro-gaps, good wetting of the different surfaces and rapid hardening,where possible.

This rapid hardening can be obtained, for instance, by the fact that thesealant has to be applied in a liquid state and can subsequently behardened by UV radiation.

As already mentioned before, the sealant is used especially between aplastic component and a metallic component in an inflator. A preferredembodiment is the additional sealing between a base of an igniterconsisting of plastic material and the adjacent housing part of theinflator which is usually made of metal. The inflator according to theinvention shows the sealant in the transition area between the base andthe housing part.

The base can be formed by injection-molding around the metallic part.

Preferably, also a pre-fabricated igniter is embedded in portions of thebase, which is effectuated especially during injection-molding.

Moreover, the base preferably forms a holder for the igniter plug, i.e.the igniter plug which is plugged onto the contact pins is held in thebase itself.

The part consisting of metal can be an external housing part of theinflator. The sealant is applied to the parts from outside after theyhave already been interconnected and not during connection of the parts.

The part consisting of metal is injection-molded, for instance, to theedge of an orifice in the external housing part, especially for closingthe latter.

The sealant is furthermore applied to the inflator preferably notextensively but only at the transition edge of the abutting parts. Forprotecting the sealant, the latter is introduced especially in a recessprovided at the transition of the abutting parts. The sealant can fillthe recess completely or almost completely. Preferably the sealant doesnot protrude outwardly vis-à-vis the recess. Especially the recess isformed by two abutting radii of the two neighboring parts which form arolling V-shaped groove.

A preferred embodiment of the invention provides that the sealant is anadhesive, especially acrylate adhesive.

The preferred mechanical, chemical and physical properties of thesealant are stated in the claims, wherein it is emphasized that one ormore of the stated properties should be given.

When applying the sealant it is important that it is applied to allrequired predetermined positions. In accordance with a preferredembodiment and in accordance with a method according to the invention itis provided that the sealant contains a dye, especially a fluorescentdye by means of which the extension of the sealant can be controlled.The color in the sealant should be clearly different from the color (ifprovided) of the plastic material of the part or, more generally, theparts to which the sealant is adjacent.

The extension of the application of the sealant can be checked evenautomatically via a camera, where appropriate.

When using a fluorescent dye the sealant, and more exactly speaking thebead formed by the sealant, is irradiated with UV light, which permits aparticularly simple, fully automated control.

The invention provides, moreover or in addition to the afore-mentionedfeatures, an inflator, especially according to the type described beforeand/or hereinafter, in which an excellent filtering effect is obtained.For this purpose, upstream of discharge orifices of the inflator anannular, preferably substantially cylindrical filter is provided in theinflator which has two axial ends. The filter extends outwardly bent,especially linearly bent at one of its axial ends. This bending of thefilter, which is produced already during manufacture of the filter andnot as late as during mounting by applying a tension force, impartshigher elasticity to the filter in the axial direction. In this way, thefilter can adapt very well to its adjacent walls during mounting intothe inflator and allows a safe, exactly predeterminable pre-tensioningforce. Thus, it is ensured with the constantly present tolerances thatthe filter also contacts the walls and no clearances which might causeleakage flows occur between the filter and the adjacent wall.

In the bent portion the filter has especially the same thickness as in acentral portion which is adjacent to the bent portion. This is toimprove the elasticity and moreover is to reduce the constructed spaceand the weight. Moreover, when manufacturing the filter no longer thewire length and thus the mass has to be transported or integrated in aparticular portion so that the bending can be simply brought about by aplastic deformation.

Preferably, the filter wall extends, viewed in axial cross-section,substantially S-shaped between the ends, wherein the bending is part ofthe “S”. This, too, is to serve for increasing the elasticity. TheS-shape relates to the built-in state in which the filter is positionedin the inflator in a preferably axially braced manner.

Especially good positional fixing as well as sealing is resulting fromthe fact that the bent portion is adjacent to a corner portion of theinflator formed by a circumferential wall and a bottom. The filter canbe positioned laterally but also axially and biased, where appropriate,via the corner portion.

The filter is laterally spaced apart especially from discharge orificesprovided in an external housing of the inflator so that a chamber can beformed ahead of the discharge orifices which permits a flow through theentire filter portion and not only through the portions of the filterpositioned directly ahead of the discharge orifices.

For obtaining the axial stability and for improving the sealing effectat the edge of the filter, for instance at an axial end, preferably atthe end opposed to the bent end, the filter can be tapered. Suchtapering can be obtained by plastic deformation of the filter or byintroducing less material in this portion. In particular, however, thetapered end should be relatively resilient so that it can optimallyadapt to the adjacent wall during mounting in the inflator.

The filter is adjacent at its axial ends, especially at the end faces,to the inflator parts. The radially innermost contact point of the bentend should preferably be located at the associated inflator partradially further outwardly than the radially outermost contact point ofthe opposed axial end at the associated inflator part. This means thatin axial direction when axially bracing the filter the contact faces arelaterally offset so that a slight bending is possible. In this way, too,the axial elasticity is to be improved.

The filter preferably consists of a wire mesh having wires ofsubstantially equal cross-section. According to another preferredembodiment, the filter can also be made of wires having differentthicknesses. Usually the filters are knitted wires.

When the filter has a tapered axial end, said tapered portion can beformed especially simply by integrating a larger length of thin wiresrelated to the volume than in the neighboring portion so that saidtapered portion also becomes softer.

The invention further relates to an inflator, especially according tothe type described before and/or hereinafter which excels by a rapidignition of its pyrotechnic material. This is obtained with an inflatorhaving at least one igniter, especially in the form of a pre-fabricatedcomponent (squib as it is called). Pyrotechnic material disposed in acombustion chamber is ignited directly or indirectly via at least oneoverflow orifice by activating the igniter.

The gas and the hot particles flowing either directly from the igniteror from the igniter and a booster charge into the combustion chamberignite the pyrotechnic material there.

In accordance with the invention, it is provided that after activatingthe igniter for igniting the pyrotechnic material such overflow orificeis movable or is moved relative to the former. The igniting gas, as itis called, and the hot particles consequently do not flow at a fixedposition of the so-called propellant into the same but brush differentportions of the propellant during the igniting operation so that theigniting area is increased on the whole. This improves the igniting rateand thus ensures a more rapid increase in pressure.

The relative movement between the overflow orifice and the pyrotechnicmaterial, the so-called propellant, can be caused by relative movementsof the propellant or else, preferably, by a movable wall. The movablewall includes the overflow orifice or orifices and moves, so-to-speak,along the propellant and is movable relative to the latter.

In accordance with an embodiment, an intermediate chamber is providedbetween the igniter and the combustion chamber. This intermediatechamber can receive, for instance, a booster charge or else can befilled with ignitable gas. Said intermediate chamber is separated fromthe combustion chamber by a cap. The cap is provided with the overfloworifice(s) and is arranged in the inflator such that it is movable byactivating the igniter or that it is moved after activating the igniter.

A further peculiarity of the inflator according to the invention, whichcan be employed in combination just as the other peculiarities solely ortogether with one or more other ideas especially according to the typedescribed before and/or hereinafter, ensures easy or simplifiedmanufacture of the inflator. The latter includes at least one igniter,especially in the form of a pre-fabricated component and an intermediatechamber (especially receiving a booster charge). Said intermediatechamber is preferably arranged, as already explained, between theigniter and the combustion chamber. This means that the intermediatechamber is adjacent to the igniter and the ignition gas of the igniterflows into the intermediate chamber. The intermediate chamber itself isconfined by a cap pushed onto a base with its igniter-side open end. Inthe case of previous caps, they are frequently pressed and beaded in abore of a very massive part or are welded to a base, which requires morecomplicated manufacture, as a matter of course, than pushing onto a baseprovided anyway.

The cap can be pressed with or onto the base and/or can be disposed atthe base such that it is movable or is moved when activating theigniter. The moving force required to move the cap can be applied by theigniting gas when activating the igniter or else by the igniting gas ofthe igniter and the additional gas generated in the intermediatechamber.

In the non-activated state of the inflator, the cap preferably should beadjacent at the end face to a resilient component, especially to aresilient packing. Resilient packings at the edge of or in thepropellant bed are preferred to pretension the bed of pyrotechnicmaterial (chaotic bed). In this context, the resilient packing has adouble function, as it serves as volumetric balancing member and,simultaneously, as a stop and more exactly speaking as a movable stopfor the cap. In order to obtain an improved compactness, the packing mayhave a recess into which portions of the cap project. During itsmovement the cap can compress the resilient component so that only inthis way the movement path is made possible.

The resilient component can also additionally be in the form of afilter, especially made of knitted mesh.

It is also taken into consideration that the resilient component ispreferably adjacent to the inside of a front wall of the inflator.

The base is formed, for instance, by injection-molding around theigniter and is preferably provided to fix the igniter at the inflator.

In accordance with an embodiment, the cap forms a partition between theintermediate chamber and a combustion chamber which is preferably filledwith pyrotechnic material. The cap can be the only partition betweensaid chambers.

The cap has at least one, preferably plural lateral overflow orifice(s)uniformly spaced at the circumference.

Inflators are activated by transmitting an electric pulse throughcontact pins accessible from the outside of the inflator to an igniterdisposed inside the external housing of the inflator.

The fast and tight, especially moisture-tight, connection must beensured over the entire service life of the inflator.

In another aspect of the invention the inflator, especially according tothe type described before and/or hereinafter, includes an externalhousing, preferably having a central axis, and an igniter embedded in abase, the external housing or a part connected to the external housingincluding a recess into which the base extends. The wall forming therecess has portions bent radially inwardly and has an outwardlyextending bulge distant from the port of the recess. In this way a typeof undercut is formed in which the material of the base extends radiallyfurther outwardly than the wall of the external housing or, in the caseof a non-integral design, the part connected to the external housing inthe port area. Thus the base and the igniter are additionally secured.

The bulge can be annularly circumferential, preferably relative to thecentral axis. It is also possible, however, to provide individual bulgesonly at individual positions along the circumference of the recess.

The wall forming the recess preferably has, adjacent to the bulge, thesame wall thickness as in the bulged portion, i.e. the wall is bent as awhole and the contour at the inside follows the one at the outside.

Viewed in an axial section, the recess may be S-shaped, wherein themouth portion of the wall forming the recess extends outwardly.Preferably no sharp edges or transitions are provided but a uniformrounding of the inner wall of the recess. In this way, the plasticmaterial forming the base can easily fill the bulges duringinjection-molding.

The invention moreover provides an inflator, especially according to thetype described before and/or hereinafter, comprising an externalhousing, preferably having a central axis, and a pre-fabricated igniterembedded in a base, the external housing or a part connected to theexternal housing having a recess into which the base extends, and a wallforming the recess having a bottom portion including an orifice throughwhich the base extends, wherein the bottom portion has at least oneprojection and/or one indentation on its opposed outsides in the area inwhich the base is adjacent to the same. This design ensures, apart froma fast connection, also an improved tightness against possible moisturepaths from outside.

For example, the edge of the orifice may have a convex projection at anoutside. In this context, “outside” means the side facing the outside ofthe inflator.

The projection can be formed by a circumferential bead, for instance. Itis possible that at this position the wall thickness of the bottomportion is increased.

The bottom portion is formed, e.g., by a part or portion of a closingmember which, in turn, is part of the external housing of the inflator.But for this purpose also a separate part of the inflator can beprovided.

The bottom portion preferably has an especially annularlycircumferential indentation at the outside opposed to the projection inthe area of the projection. This indentation is directed into theinterior of the inflator, for instance.

Both the projection and the optional indentation are advantageouslysurrounded by or filled with the plastic material of the base.

This is of particular advantage when the base is formed byinjection-molding around at least portions of the wall forming therecess, because in this way a tight connection is provided.

In another aspect of the invention, an inflator according to theinvention, especially according to the type described before and/orhereinafter, comprises an external housing having at its outercircumference a flange, the flange being non-symmetrical or having ashape deviating from the symmetry in order to ensure an unambiguousmounting position at least in twisting direction when the inflator isfastened.

The non-symmetry can be advantageously obtained by the fact that atleast one notch is provided in the flange as a mounting positioningmeans. As a matter of course, also other mounting positioning meanspermitting a so-called indexing can be provided.

In a possible configuration plural, especially three, notches areprovided which are arranged at different angular distances along thecircumference of the flange. In this way the mounting position of theinflator is clearly defined by simple means.

As an alternative or in addition, a positioning orifice, especially anoblong hole, can be provided in the flange as mounting positioningmeans.

The invention also relates to a module including an inflator mentionedabove and/or hereinafter. The module has a holding member at whichpreferably a counter-piece engaging in the mounting positioning means ofthe flange is provided.

The counter-piece can at least include a projection formed at theholding member, for instance.

It is possible that the holding member has at least one fastening bolt,the latter being adjacent to the outer circumference of the flange.Preferably the fastening bolt is not adjacent to the flange in the areaof the mounting positioning means but is distant hereof.

The module can be especially an airbag module but can also be adifferent assembly including an inflator, for instance a tensioningdrive.

If the module is an airbag module in which an airbag having an inletorifice is provided, the edge of the inlet orifice is advantageouslyclamped between the flange and the holding member.

The invention further relates to an inflator, especially according tothe type described before and/or hereinafter, comprising a combustionchamber filled at least partly with pyrotechnic material which isconfined by combustion chamber walls, wherein all combustion chamberwalls consist of the same material, especially of the same steel.

A combustion chamber wall must have a particular inherent stability sothat it is not completely destroyed after activating the inflator duringignition of the pyrotechnic material. The pyrotechnic material isdirectly adjacent to said stable combustion chamber walls and thuscontacts the combustion chamber walls in some cases for many yearswithout any chemical variations being intended to occur. The inventionprovides that all combustion chamber walls consist of the same metal,especially steel. So far the combustion chamber walls have beenmanufactured of different materials mainly by virtue of their differentloads. The invention simplifies the concept of an inflator, for theso-called propellant compatibility with adjacent components is ensured,if actually all combustion chamber walls consist of the same material.Thus only a material pairing of pyrotechnic material with combustionchamber material has to be tested. It is especially preferred that alsopossible walls delimiting the combustion chamber against the igniterand/or against the intermediate chamber are formed of the same material,especially of steel, and especially of the same steel.

The combustion chamber walls are especially plural interconnected parts,these parts especially being load-bearing components. Load-bearingcomponents are those components which are still retained aftercombustion of the pyrotechnic material.

In this context and also in connection with other peculiarities of theinvention mentioned before and hereinafter, it is emphasized that theinflator according to the invention especially is an inflator having anannular chamber in the form of a combustion chamber. Such inflators arealso referred to as toroidal inflators.

It is another characteristic of the inflator according to the inventionthat its axial height is less than its diameter. Inflators of this typeare integrated in particular in steering wheel airbag modules.

Another aspect of the invention provides that an inflator according tothe invention, especially according to the type described before and/orhereinafter, includes an external housing and a combustion chamberarranged inside the external housing which contains pyrotechnicgas-generating material, wherein the wall thickness of the componentparts, especially of the metallic component parts, of the externalhousing is 2 mm or less. This saves weight.

The external housing can consist of a diffuser and a closing member, thediffuser and the closing member preferably being cup-shaped. Thediffuser and the closing member can be fitted into each other, whereinan upwardly bent edge of the closing member is located inside theespecially pot-shaped diffuser and is adjacent to the inner wall of thediffuser.

The closing member and the diffuser can be fastened to each other by onesingle connection defining the strength, i.e. no tension rod or the likeis provided. The connection is in particular a circumferential weldbetween the diffuser and the closing member. The weld can be formed,e.g., by laser welding. In other words, the wall thickness of theexternal housing thus is in total 2.0 mm or less, wherein an overlappingarea of the parts forming the external housing (especially in the areaof the joining weld) is left out of consideration.

Preferably the wall thickness of the diffuser amounts to a maximum of2.0 mm, 1.9 mm, 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm,1.1 mm or 1.0 mm. Further preferably the wall thickness of the closingmember amounts to a maximum of 3.0 mm, 2.9 mm, 2.8 mm, 2.7 mm, 2.6 mm,2.5 mm, 2.4 mm, 2.3 mm, 2.2 mm, 2.1 mm, 2.0 mm, 1.9 mm, 1.8 mm, 1.7 mm,1.6 mm, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm, 1.1 mm or 1.0 mm. In this waythe inflator can be designed more easily and the total energy range ofthe vehicle can be optimized.

It is preferred that upon activation the inflator develops a maximumcombustion chamber pressure of 360 bar, 340 bar, 320 bar, 300 bar, 290bar, 280 bar, 270 bar, 260 bar or 250 bar which the walls have towithstand. In this way, the entire configuration of the inflator and ofthe module can be optimized and the manufacture can be made moreinexpensive.

The combustion chamber preferably has a substantially toroidal shape,wherein especially in the center of the toroid the igniter is arrangedand a booster charge is possibly arranged in an intermediate chamber.

Preferably the ratio of the maximum combustion chamber pressure formedupon activation of the inflator to the wall thickness of the externalhousing is more than 120 bar/mm, especially more than 130 bar/mm, 140bar/mm, 150 bar/mm, 160 bar/mm, and/or 170 bar/mm. Further preferablythe ratio of the maximum combustion chamber pressure formed uponactivation of the inflator to the wall thickness of the external housingis less than 250 bar/mm, especially less than 240 bar/mm, 230 bar/mm,220 bar/mm, 210 bar/mm, 200 bar/mm, 190 bar/mm and/or 180 bar/mm.

The ratio of the entire discharge area of the inflator, viz. of theentire area of all discharge orifices of the inflator, to the wallthickness of the external housing preferably is more than 27, 28, 29,30, 31, 32 or 33 mm. The ratio of the entire discharge area of theinflator, viz. of the entire area of all discharge orifices of theinflator, to the wall thickness of the external housing preferably ismore than 32, 33, 34, 35, 36 or 37 mm.

The ratio of the diameter of the diffuser to the smallest wall thicknessof the external housing preferably is smaller than 50 and/or larger than30, preferably between 31 and 49, especially between 32 and 48,especially between 33 and 47, especially between 34 and 46, preferablybetween 35 and 45. The projecting fastening flange is not added whenmeasuring, but only the inflator part defining the hollow which isformed by the external housing has to be measured. The diffuseradvantageously has a substantially cylindrical circumferential wall.

The ratio of the diameter of the diffuser to the maximum axial height ofthe inflator preferably is about 1.8±0.7, especially 1.8±0.5, especially1.8±0.4, further preferably 1.8±0.3, especially 1.8±0.2, preferably1.8±0.1.

It is not necessary to use a tension rod, i.e. an additional connectionbetween the upper and the lower area of the external housing, but it ispossible as an option.

The inflator preferably has a flat cylindrical shape and thus its widthis larger than its height.

The present invention provides further peculiarities which may beprovided in addition to or separately from the characteristics andfeatures mentioned before and hereinafter.

In addition, the constructed space of an inflator is to be reduced. Inthis respect, the invention provides various options which can beemployed individually or in combination.

The external housing of the inflator, especially according to the typedescribed before and/or hereinafter, includes a flange provided at itsouter circumference which is circumferentially closed. Said flange ispreferably planar and is transformed in a transition area, whichhereinafter shall not be added to the flange, with a radius into theactual external housing. That is to say, the flange is transformed intothe external housing. Concerning the flange width the radius is notadded in the following.

According to an idea, the flange is formed without through-holes.Through-holes reduce the clamping area between the flange and anadjacent component, especially an airbag clamped to the flange, so thatmore support area and thus clamping area is provided without thethrough-holes. Since the airbag includes an inlet orifice with anorifice edge which is especially coated, for instance with silicone, theflange can establish sort of an adhesive or glued connection with theorifice edge. The missing through-holes increase the displacing forcerequired to displace the airbag.

It is another or an additional possibility that the airbag and theflange have a joint annular clamping area that features a width between5 and 12%, preferably between 6 and 11%, further preferably 8 to 10% ofthe maximum diameter of the external housing of the inflator. Thediameter of an inflator reveals a lot about the generated gas volume,which in turn allows concluding therefrom the pressure exerted on theairbag and the displacing force of the airbag. A minimized flangediameter is obtained by reducing the flange width to the predeterminedvalues.

Another or an additional option provides that the annular clamping areafor the airbag has a width at the flange which ranges from 6 to 9.5 mm,preferably from 5 to 8.5 mm, further preferably from 5.5 to 7.5 mm. Thissmall width is clearly different from previous flange widths.

For minimizing the flange an airbag module according to the inventionmay be provided which includes an inflator, especially anafore-mentioned inflator, which at its external housing and the outercircumference thereof has a flange, an airbag with an injection orificedefined by an orifice edge and a clamping member opposed to the flange.Said clamping member can be a separate ring or a separate component, forinstance a diffuser cage or the like or an inflator carrier in order toclamp the orifice edge between the same and the flange. The clampingforce is adapted in the area of the orifice edge and the clamping areasuch that the lateral displacing force occurring by the maximum pressurein the airbag at the orifice edge is between 10 and 80%, preferablybetween 20 and 50% less than the friction force generated by theclamping force between the orifice edge, the flange and the clampingmember. This relatively simple design is sufficient, as it has turnedout, to minimize the clamping flange.

The afore-mentioned airbag module or an airbag module according to theinvention deviating herefrom provides that in the clamped portion of theorifice edge the airbag has only an opening serving for circumferentialpositioning, if at all. Consequently, no clamping orifice is providedthrough which a respective screw extends. Holes in the area of thecircumferential edge of the airbag weaken the airbag fabric and reducethe support surface. An aspect of the invention provides that suchweakening is avoided and instead the larger surface of the orifice edgeis provided for clamping.

It has to be emphasized that the individual features mentioned beforeand in the following description can be combined in any way. Theinvention is not restricted to be realized in individual features or ingroups of features only.

In accordance with a further aspect of the invention, the inflator,especially according to the type described before and/or hereinafter,has an external housing including a diffuser with a substantiallycylindrical circumferential wall having plural discharge orifices and aclosing member welded with the diffuser, wherein the diffuser and theclosing member are preferably cup-shaped and wherein the dischargeorifices are covered at the inside of the diffuser by a tamping,preferably in the form of a tamping film, and the tamping is spacedapart from the inner edge of the closing member, especially a weld,preferably a laser weld, between the diffuser and the closing member.This design has the advantage that the tamping is protected in laterassembly steps and therefore is not thermally affected especially inwelding processes during which heat is developed.

Preferably the distance is more than 2 mm, especially preferred it ismore than 2.5 mm, especially more than 3 mm. The distance preferablyamounts to less than 7 mm, especially preferably it is less than 6 mm,in particular less than 5.5 mm. Thus the distance preferably ranges from3 to 7 mm and further preferably from 3 to 5.5 mm.

The closing member may have a circumferential upright edge to which itis welded with the diffuser, and the smallest distance of the weld fromthe tamping amounts to at least the afore-mentioned distance values. Inthis way a robust and good tamping of the discharge orifices of theinflator can be achieved.

As mentioned already it is important that the igniter is arrangedfixedly and tightly in the inflator and remains so during the entireservice life of the inflator.

According to the invention, this object is achieved by the fact that theinflator, especially in accordance with the above and/or below describedtype, includes an igniter having an igniter cap which is at least partlysurrounded by plastic injection-molding, the material of the igniter capand the material of the plastic molding being selected such that duringinjection molding the igniter cap at least partly melts into the plasticinjection molding, i.e. partial melting of the cap is also included.

In this way, an especially tight and fast connection is obtained betweenthe plastic injection molding and the igniter.

The igniter cap can be part of the igniter itself which is preferablysupplied as a pre-fabricated part or it can be a separate componentwhich is attached onto the igniter before the latter is surrounded byinjection molding.

Preferably, the igniter cap and the plastic injection molding consist ofthe same material. This material may contain glass fibers, the glassfiber share preferably being approx. 20-40% by weight and especiallypreferred being approx. 30%.

The plastic injection molding of the igniter advantageously forms thebasis by which the igniter is connected to the external housing. Thiscould also be a different component, however, which is finally in turnconnected to the external housing in order to tightly connect theigniter to the external housing.

The external housing preferably includes an orifice and the plasticmaterial is injection-molded around the edge of the orifice, inparticular to seal the external housing to the outside.

Furthermore, the invention relates especially to an inflator, preferablyfor a vehicle occupant restraint system and preferably according to theabove and/or below described type, comprising a first component and asecond component which is connected to the first component through aninjected plastic base in that both components are at least partlysurrounded by injection molding. The invention further relates to amethod of manufacturing an inflator.

In a conventional inflator the first component, for instance, is a coverof a generator housing which is connected to the second component, viz.an igniter, in that the igniter is arranged in an orifice disposed inthe cover and both parts are jointly surrounded by injection molding. Inthis way, a simple connection is provided between the igniter and thegenerator housing which excels by low weight and low manufacturingcosts.

It is intended according to the invention to provide an inflator or amethod for manufacturing an inflator in which the junction of thecomponents has improved tightness.

In accordance with an aspect of the invention, in an inflator of saidtype it is provided that the first component has an adhesive filmapplied before injection molding in a contact area with the plasticbase. A particularly tight connection between the plastic base and thefirst component is achieved by the adhesive film. In contrast to asealing formed by shrinking a plastic material, in the inflatoraccording to the invention the first component may have almost anygeometry, wherein additional geometrical elements for increasing thetightness, such as undercuts or injection moldings around parts, can bedispensed with. Also additional components such as a metallic filmserving as bar to moisture or an annular packing are not required.Therefore, the inflator according to the invention can be manufacturedin an especially simple and inexpensive manner.

The first component preferably consists of metal, ceramic and/or plasticmaterial.

As mentioned already in the beginning, the first component preferably isan inflator housing or forms a partial element of an inflator housing.

The second component especially is a pre-fabricated igniter closed tothe outside. This igniter in general has a metallic outer shell so thatit may be advantageous when also the igniter (or only the igniter whichthen has to be regarded as first component) is provided prior toinjection molding with an adhesive film forming a bonding bridge.

A particularly simple joining of the components results from the factthat the first component has an opening for receiving and mounting thesecond component whose edge is embedded in the plastic base duringinjection molding. In the case of an igniter as second component, theelectric connections thereof can project from the first component,especially the inflator housing, through the opening.

In accordance with a preferred embodiment of the invention, the surfaceof the adhesive film exactly corresponds to the contacting surfacebetween the plastic base and the first component, whereby an improvedadhesion of the plastic base to the first component is ensured all overthe surface.

Depending on the shape of the first component, it may be sufficient,however, when the surface of the adhesive film is smaller than thecontacting surface between the plastic base and the first component. Inthis way, too, a reliable sealing can be achieved already in many cases.

Another variant of the invention provides to design the surface of theadhesive film to be larger than the contacting surface between theplastic base and the first component. Then the adhesive film in additionserves as an anti-corrosive layer.

Advantageously the adhesive film is a pre-fabricated part. It can beapplied like a known tamping film.

Preferably the adhesive film includes a plastic film and an adhesivelayer. The adhesive layer is advantageously applied directly to theplastic film. The adhesive film can be glued with its adhesive side ontothe first component so that the adhesive layer keeps the adhesive filmfixed to the metallic first component during injection molding. Theplastic material introduced during injection molding gets into contactwith the plastic film which protects the adhesive film disposed therebelow against the high temperatures.

Advantageously the plastic film consists of the same material as theplastic base or of a material which is suited to establish a connectionwith the material of the plastic base.

Preferably the plastic film melts into the plastic base when the plasticbase is injection-molded. Along a joining zone a fixed connection isformed between the adhesive film and the plastic base. As analternative, the fixed connection can also be brought about by achemical reaction of the material of the plastic base with the materialof the plastic film.

The adhesive film, especially the adhesive layer, preferably forms abonding bridge between the first component and the plastic base which ofadvantage is plastically and/or elastically deformable. In this way,tensions and shearing forces occurring upon a change of temperature dueto different expansion forces of the materials can be compensated.

The adhesive can be applied to the plastic film in an exactly defined,for instance constant layer thickness.

The adhesive of the adhesive layer can be activated or hardened e.g. bya predetermined contact pressure or a thermal influence. For thispurpose, for instance the contact pressure during gluing or the thermalinfluence by the liquid plastic material used during injection moldingcan be exploited.

As material for the plastic film e.g. a thermoplastic elastomer (TPE) istaken into consideration.

In accordance with a second aspect of the invention, a method ofmanufacturing an inflator, especially for a vehicle occupant restraintsystem, is provided, the method comprising the following steps. First ofall, a first component containing metal and/or ceramic and/or plasticmaterial and a second component to be connected to the first componentare provided. Subsequently, an adhesive film is applied to the firstcomponent in a joining area, and the second component is positionedrelative to the first component. The first and second components arejointly surrounded at least partly by injection molding, thereby aplastic base connecting the components being formed. As alreadydescribed with respect to the inflator according to the invention, thefirst component preferably is an inflator housing or part thereof andthe second component is a pre-fabricated igniter.

Preferably the plastic film of the adhesive film melts into the plasticbase when the two components are surrounded by injection molding.

Moreover, also all advantageous further developments mentioned withrespect to the inflator apply to the method according to the invention.

Furthermore, the object underlying the invention is to improve a modulecomprising an inflator, an airbag inflatable by the inflator and amounting means for mounting the module, especially in the interior of avehicle, in such way that the manufacturing costs thereof can bereduced.

This object is achieved for such module according to the invention bythe fact that the inflator is formed in accordance with at least any oneof the claims to 1 to 103.

Further features and advantages of the invention result from thefollowing description of plural preferred embodiments in connection withthe enclosed drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of an inflator according to the invention;

FIG. 2 is a detailed view of FIG. 1;

FIG. 3 is another detailed view of FIG. 1;

FIG. 4 a is a schematic plan view of the flange of an inflator accordingto the invention;

FIG. 4 b illustrates a variant of the flange shown in FIG. 4 a;

FIGS. 5 and 6 show schematic perspective views of an airbag supportingsheet of a module according to the invention, especially an airbagmodule, comprising a mounted inflator according to the invention;

FIG. 7 is a schematic cross-sectional view of an airbag module accordingto the invention comprising an inflator according to the invention;

FIG. 8 is a schematic perspective representation of a diffuser of aninflator according to the invention;

FIG. 9 is a schematic sectional view of the diffuser shown in FIG. 8;

FIG. 10 is a sectional view of an inflator according to the invention;

FIG. 11 is an enlarged detail of FIG. 10 showing the connection of afirst and a second component; and

FIG. 12 is an enlarged illustration of the transition from the first tothe second component.

FIG. 1 shows an inflator 10 comprising an external housing 12 beingcomposed of a cup-shaped diffuser 14 having a substantially cylindricalcircumferential wall 16 and a closing member 18 which also forms thebottom of the inflator 10.

The closing member 18 includes a circumferential upright edge 20 whichis adjacent to the inside of the circumferential wall 16 of the diffuser14 and is fixedly connected to the same by way of a weld 22. The weld 22preferably extends along the entire contact surface between the closingshell 18 and the diffuser 14 and to the outside of the inflator 10,where it fills a groove existing between the closing member 18 and thediffuser 14. For connecting the diffuser 14 and the closing member 18 alaser welding method can be used, for instance.

At the closing member side end, the circumferential wall 16 of thediffuser 14 is bent outwardly so that a planar flange 24 beinghorizontally circumferential along the inflator 10 is formed.

The closing member 18 has a central orifice 26 which serves forreceiving a pre-fabricated igniter 28. The closing member 18 has arecess 34 including an annular portion 30 toward the central orifice 26.The recess 34 is sort of an inversion of the external housing. This areaof the inflator 10 is illustrated in detail in FIGS. 2 and 3.

The igniter 28 is enclosed by a base 32 connecting the igniter 28 alsoto the closing member 18 and especially to the edge of the orifice 26and the annular portion 30.

The base 32 consists of plastic material and is injection-molded afterintroducing the igniter 28 into the orifice 26. During injection-moldingthe plastic material encloses both the major part of the igniter 28 andthe edge of the orifice 26 and also completely fills the recess 34formed by the annular portion 30 at the outside of the inflator 10 withthe exception of an outwardly directed igniter plug receipt 38 intowhich the contact pins for an electric contacting of the igniter 28protrude. The igniter 38 is simultaneously embedded in the base 32during injection molding. The orifice 26 is completely closed by thebase 32 and the igniter 28 and the recess 34 is so-to-speak lined by thebase.

In this case the igniter 28 is enclosed by the base 32 so far thatmerely its upper side as well as a short upper portion of an igniter cap36 are left open.

The igniter 28 preferably is a separate pre-fabricated component. Theigniter cap 36 is either part of the pre-fabricated igniter 28 or aseparate component placed onto the igniter 28.

The igniter cap 36 in this example consists of plastic material, namelyof a plastic material similar to that of the base 32, preferably of anidentical plastic material. A standard material having a share of glassfiber is preferably used, wherein the glass fiber share may be, forinstance, 30% by weight. The use of a similar or identical plasticmaterial entails the fact that during injection-molding the igniter cap36 melts completely or partly with the base 32 and in this way a tightand non-detachable connection is formed.

The recess 34 can also be formed at a separate part of the inflator 10which is connected to the external housing 12, especially to the closingmember 18.

At the outside of the recess 34 a circumferential indentation is formedbetween the closing member 18 and the base 32, which indentation isfilled with a sealant 42, in this case in the form of an acrylateadhesive.

The sealant 42 is selected such that it adheres both to the metal of theclosing shell 18 and to the plastic material of the base 32. The sealant42 is applied from outside after injection molding of the base 32 and islocated completely outside the external housing 12 of the inflator 10and completely in the circumferential indentation.

The sealant 42 is applied in liquid or pasty form and is hardened by UVlight. It has high flexibility also at low temperatures of up to −40° C.It features low viscosity so that it is easy to process, has goodwetting properties both for metallic and for plastic surfaces andadheres both to metal and to plastic material.

The sealant has at least one of the following properties:

Breaking strength according to ISO 527 [MPa] 2-4, esp. 3;

Elongation at break according to ISO 527 [%] 200-400, esp. 300±40;

Viscosity at 23° C. according to Brookfield Sp/U and 3/100 [mPas]400-800, esp. 600±80;

Glass transition temperature (rheometer) [° C.] 10-30, esp. 20±4;

Thermal expansion coefficient at 30-140° C. [ppm/K] 150-350, esp.260±30;

Density at 23° C. [g/cm3] 0.6-1.5, esp. 1.0±0.1;

Water absorption according to ISO 62, 24 h at 23° C. [%] 0.9-1.7, esp.1.3±0.2.

A dye, preferably a fluorescent dye, is added to the sealant 42. Thispermits simple control whether the sealing bead has been completelyapplied and the recess is completely filled with the sealant 42. Whenirradiated with UV light, it can be easily recognized due to thefluorescent dye at which position the sealant 42 is provided. If anon-fluorescent dye is used, for the same a color other than for thebase 32 and the closing member 18 is chosen so that it can be recognizedby way of the color whether the sealing bead is complete andcircumferential.

This can be checked using a camera.

Prior to mounting into an airbag module, the contact pins 40 of theinflator 10 are connected via a short-circuit bridge 44. The igniterplug receipt 38, the base 32 and the sealant 42 are covered in thisstate by a laminate film 46 and are protected against environmentalinfluences in this way.

The wall forming the recess 34 is arc-shaped in portions in the radialdirection r (cf. FIG. 3) in such a manner that one or more bulges 48extending in radial direction away from the recess 34 are formed. Theinflator 10 has a central axis A (cf. FIG. 1). Relative to this centralaxis A the arc forming the bulge 48 in this example extends in ringshape around the recess 34.

It is also possible to form the bulge 48 in circumferential directionintermittently and to provide only one or more separate bulges 48 alongthe circumference of the recess 34. The extension of the wall is shownin broken lines in FIG. 3. The wall thickness of the wall of the recess34 is unchanged in this case vis-à-vis the wall thickness outside thebulge 48.

In the section shown in FIG. 3 the wall of the recess 34 forms anS-shaped curve in the area of a bulge 48, the opening portion (loweraxial end) of the wall forming the recess 34 extending outwardly.

Apart from the annular portion 30, the recess 34 includes a bottomportion 50 which is connected to the annular portion 30 toward theinterior of the inflator 10. The bottom portion 50 also forms the edgeof the orifice 26. At the bottom portion 50 an annularly circumferentialprojection 52 is formed at the edge of the orifice 26 toward the outsideof the inflator (provided with reference numerals only in FIG. 3). Theprojection 52 forms a convex shape and is shaped without any sharpedges. On the opposed side (inner side) the bottom portion has anindentation preferably rectangular in profile which extends equallycircumferentially along the edge of the orifice 26 and whose orifice isdirected toward the interior of the inflator 10.

Both the groove 54 and the projection 52 are enclosed by liquid plasticmaterial when the base 32 is injection-molded so that a fast and tightconnection to the base 32 is formed which also withstands temperaturevariations and constitutes an additional support during and aftersolidification of the plastic material. Also the groove 54 is shown withreference numeral in FIG. 3 only.

Inside the external housing 12 an annular, thus substantially toroidalcombustion chamber 56 is formed (cf. FIG. 1) which is filled with aknown pyrotechnic gas-generating agent 58, indicated by some tablets inthis case.

Toward the central axis A of the inflator 10, the combustion chamber 56is confined by a cap 60 enclosing the igniter 28 and the portion of thebase 32 located inside the inflator 10 as well as in addition a freespace in the form of an intermediate chamber 62. The intermediatechamber 62 is filled with a boosting charge of known pyrotechnicgas-generating material 64.

The cap 60 (cf. FIG. 2) has plural overflow orifices 66 providing acommunication between the intermediate chamber 62 and the combustionchamber 56. In this example, the cap 60 is made of steel. It is closedat the upper end and open at the lower end and has a substantiallycylindrical wall in which the overflow orifices 66 are disposed. The cap60 is outwardly bent at the open end so that a short flange 68 is formed(cf. FIG. 2). After introducing the boosting charge 64, the cap 60 ismerely pushed onto the base 32 and is possibly pressed with the same orpushed onto the same forming a press-fit. Fastening by welding is notprovided. This leads to the fact that, when activating the inflator 10and igniting the igniter 28, the cap 60 can move in the upwarddirection, i.e. away from the igniter 28. In this way, in the course ofthe burning operation also the overflow orifices 66 move upwards, i.e.relative to the propellant. Thus further portions of the propellant bedin the combustion chamber 56 contact the hot gases flowing out of theintermediate chamber 62 and are ignited.

The upper portion of the combustion chamber 56 in FIG. 1, viz. at theside of the external housing 12 opposed to the igniter 28, is providedwith an elastic component 70, in this case a filler or volumecompensating element which contacts the upper side of the diffuser 14.The elastic component 70 is formed of a wire mesh here and can becompressed when the cap 60 moves. Further moving space for the cap 60 isgained from the bulge of the inflator 10 during gas formation duringwhich the upper side of the diffuser 14 is slightly raised.

The elastic component 70 has a central recess 72 into which the capprotrudes up to a step and whose upper end portion is somewhat smallerthan the diameter of the cap 60 in order to counter the movement of thecap 60 by a defined moving resistance.

In this case the cap 60 constitutes the only partition wall between theintermediate chamber 62 and the combustion chamber 56. It is possiblethat the inside of the cap 60 is lined with a protective film 74 closingthe overflow orifices 66 prior to activation of the inflator 10, whereinthe protective film 74 is destroyed upon ignition of the igniter 28.

In the state before activation shown in FIG. 1, the overflow orifices 66are located directly at the upper edge of the base 32 so that they havean as large moving distance as possible in the direction of the centralaxis A.

A filter 76 is arranged in the combustion chamber 56 which in this caseis ring-shaped, substantially cylindrical and extends in parallel to thecircumferential wall 16 of the diffuser 14 at a small radial distancefrom the same.

The filter 76 extends over the entire height of the inflator 10 andextends from the closing member 18 to the end face of the diffuser 14.The filter 76 is formed of a wire mesh including wires of differentthickness.

In the circumferential wall 16 of the diffuser 14 plural, in thisexample twelve, discharge orifices 78 are formed which are uniformlyspaced along the circumference of the diffuser 14 and are arranged at anaxial height. The filter 76 separates the discharge orifices 78 from thecombustion chamber 56 so that the filter 76 is located upstream of thedischarge orifices 78.

The filter 76 is pressed into the external housing 12 with axialpre-tension.

The filter 76 includes two axial ends 80, 82 at least one end of whichis bent outwardly. In this case the bent portion forms the lower axialend 80 and the bending extends straight. In the bent portion the filter76 has the same thickness as it has also in a central portion which isadjacent to the bent portion.

In the shown example the filter 76 extends in S-shape viewed in an axialsection. At the upper axial end 82, too, a slight bending is providedwhich extends toward the center of the inflator 10, however (indicatedon the left half in FIG. 1 by broken lines).

At the filter 76 the radially innermost contacting position of theoutwardly bent lower axial end 80 is located radially further outwardthan the radially outermost contacting position of the inwardly bentaxial end 82 so that the end-face contact surfaces are laterallycompletely offset.

The bent portion at the lower axial end 80 is adjacent to a cornerformed by the housing of the inflator 10. In this case the housing partis formed by the closing member 18 and the lower axial end 80 of thefilter 76 is adjacent to the transition from a bottom plate of theclosing member 18 to the upwardly bent edge 20 of the same.

At the upper axial end 82 the filter 76 is tapered, as is visibleespecially on the right side of FIG. 1. At this end, the filter 76 has alarger length of thin wires, relative to the volume, than in theadjacent area and preferably than in the residual filter, which rendersthe tapered area very flexible.

This shaping permits to deform the material during axial pressing intothe inflator such that no bypass is formed for particles possiblyoccurring during combustion of the pyrotechnic material 58.

The pyrotechnic material 58 in the combustion chamber 56 is surroundedwith metal on all sides, i.e. the combustion chamber wall composed ofseveral parts consists throughout of the same material. The combustionchamber 56 is enclosed by the elastic filler 70, the filter 76, the cap60 and the closing member 80. As stated before, all these componentspreferably consist of the same metal, preferred of the same steel.

The discharge orifices 78 are closed prior to activation of the inflator10 by a tamping 84 in the form of a tamping film. The tamping 84 isdisposed circumferentially at the inside of the circumferential wall 16of the diffuser 14 at the height of the discharge orifices 78 and coversall discharge orifices 78. The height of tamping 84 is approximatelyfour times the diameter of the discharge orifices 78 in this case.

The lower end of the tamping 84, viz. the end facing the closing member18, is arranged at a distance from the weld 22 which connects thediffuser 14 to the closing member 18. The distance a from the weld 22,or in this case equivalent to the end of the upper edge 20 of theclosing member 18, in the shown case amounts to approx. 5.5 mm andpreferably ranges from 3 to 7 mm (cf. FIG. 1). This distance issufficient to prevent undesired heat transfer to the tamping 84 duringwelding.

The external housing 12 of the inflator 10 has a relatively thin wallthickness which in the example shown here nowhere is more than 2 mm. Inparticular, the wall thickness of the diffuser is 1.5 mm and that of theclosing member is 1.9 mm. These wall thicknesses are sufficient towithstand a combustion chamber pressure of 300 bars upon activation ofthe inflator 10.

The diffuser 14 and the closing member 18 are connected only through theweld 22 so that said weld 22 forms the only connection between thecomponents of the external housing 12 defining the strength. Preferablya tension rod is not provided.

In this case, the ratio of the maximum combustion chamber pressure tothe wall thickness preferably is between 150 and 220 bars/mm.

The ratio of the entire discharge area of the inflator 10, viz. the sumof the areas of all discharge orifices 78, to the wall thickness is morethan 30, especially more than 34 mm, in this case.

The ratio of the diameter D of the diffuser, measured by the diameter ofthe circumferential wall 16, to the minimum wall thickness of theexternal housing is preferably less than 50 and preferably ranges from35 to 45. The flange 24 is not taken into account when determining thediameter.

The inflator 10 has substantially the shape of a flat cylinder, theratio of the diameter D to the maximum axial height H being approx.1.8±0.2, preferably 1.8±0.1.

The flange 24 at the outer circumference of the diffuser 14 is planarbut unsymmetrical (cf. FIGS. 4 a and b). This design offers apositioning aid when mounting the inflator 10 into a module, forinstance an airbag module, by clearly defining the mounting position.

In the present example three notches are spaced along the circumferenceof the flange 24 as mounting positioning means 86, namely at differentangular distances. The angles between the notches amount, for instance,to 115 and 148° or to 93 and 109° in a different example.

As an additional or alternative mounting positioning means an orifice 88is formed as oblong hole in the flange 84. This orifice 88 is the onlyorifice provided in the flange 84.

As a matter of course, also more or fewer notches 86 or projectionsinstead of the notches or other suitable mounting positioning means 86can be provided.

When mounting the inflator 10 into a module, for instance an airbagmodule 90 shown in FIG. 7, the inflator 10 is fastened by a clamping orholding element 92 (cf. also FIGS. 5 to 7). The holding element 92 has acentral opening through which the inflator 10 partly extends so that theholding element 92 presses against the flange 24. The holding element 92includes corresponding mounting positioning means 94 which arecomplementary to the mounting positioning means 86 of the flange 24 ofthe inflator 10. In this case, the mounting positioning means 94 areformed by integrally provided projections in the holding element 92, forinstance in the form of cut-out and upwardly bent sheet sections. Theprojections engage in the notches and thus clearly define the mountingposition of the inflator 10.

The orifice 88 in the flange 24 serves for defining the mountingposition of an airbag 96 (indicated in FIG. 7) which is clamped betweenthe flange 24 and the holding element 92 by the orifice edge 100 of itsinjecting orifice 98.

The oblong hole 88 moreover can also be used for manufacturing theinflator. In particular, in different manufacturing steps the correctposition of the diffuser (flange) with respect to other inflatorcomponents can be ensured by a pin in the tool head which is adapted tobe engaged with the oblong hole, e.g. for orientation of the igniterpins.

The airbag 96 likewise has an orifice at the orifice edge 100 (notshown) which is made to match with the orifice 88 in the flange in orderto correctly position the airbag 96. The orifice 88 does not serve asscrewing orifice and constitutes the only orifice at the orifice edge100 of the airbag 96. This means that the airbag 96 is clamped betweenthe flange 24 and the holding element 92 by fastening means, usuallystud bolts, which are located outside the flange 24. Thus the flangesurface is optimized.

For fastening the airbag module 90 the holding element 92 includesfastening bolts 102, four of them in the shown example, through whichthe airbag module 90 can be connected to a vehicle (not shown). Thefastening bolts 102 are adjacent to the outer circumference of theflange 24 but offside the area of the mounting positioning means 86.

The flange 24 is circumferential and planar.

It forms an annular clamping surface for the airbag 96, wherein thewidth B of the flange (the transition radius between the planar flangeportion and the circumferential wall of the diffuser 14) is between 5and 12%, preferably between 8 and 11% of the maximum diameter D of theexternal housing 12.

The width B of the clamping surface in the radial direction r rangesfrom 5 to 8.5, preferably from 5.5 to 7.5 mm (cf. FIG. 9).

At the holding element 92 opposed to the clamping surface a clampingportion 104 is defined at the flange 24 (cf. FIG. 7), which clampingportion produces a holding force for the airbag 96 together with theclamping surface at the flange 24. The clamping surface and the clampingportion 104 are designed such that the forces acting via the maximuminternal pressure in the airbag 96 on the orifice edge 100 are by 20 to50% less than the clamping force produced between the clamping surfaceand the clamping element 104. The width B of the flange 24 can beconsiderably reduced, so-to-speak to the minimum flange width, by thisvery simple measure.

FIG. 10 shows a special embodiment of an inflator 110 according to theinvention which exhibits a first component 112, here made of metal, inthe form of an inflator housing in which an igniter device 113 iscentrally disposed. The latter comprises an igniter constituting asecond component 114 which is connected to the first component 112 viaan injection-molded plastic base 116 by the fact that both componentsare at least partly jointly surrounded by injection-molding. The igniterin this case is a pre-fabricated component enclosed by a metallic outershell and includes plural connecting wires 118 partly embedded in theplastic base 116 which project through an orifice 120 in the firstcomponent 112 (the inflator housing) from the latter. The orifice 120simultaneously serves for receiving and fastening the second component114 (of the igniter), wherein especially the portion of the firstcomponent 112 forming the edge 122 of the orifice 120 is embedded in theplastic base 116 during injection-molding.

The upper end of the igniter in FIG. 10 is adjacent to a booster chamber124 filled with a boosting charge. In the shown configuration a sleeve126 confining the booster chamber 124 and having plural overfloworifices 128 is placed onto the igniter or the plastic base 116. Thebooster chamber 124 is surrounded by a combustion chamber 130 which isfilled with a schematically illustrated propellant 132 in the form oftablets and at the outside is adjacent to a filter 134. At itscircumferential wall, the inflator housing has discharge orifices 136which in the mounted state are protected against penetration of moistureby a tamping film 138. Upon activation of the inflator 110, a gas isgenerated in a known way which flows to the outside through thedischarge orifices 136 and serves, e.g., for filling an airbag of avehicle occupant restraint system.

In the contacting area 140 located in the vicinity of the orifice 120 orthe edge 122 between the plastic base 116 and the first component 112,the latter is provided with an adhesive film 142 which was appliedalready before injection-molding the plastic base 116. The adhesive film142 only covers a portion of the injection-molded area of the firstcomponent 112. The adhesive film 142 is fully circumferential around theedge 122, however.

The adhesive film 142 is a pre-fabricated component and consists of aplastic film 144 and an adhesive layer 146 directly and evenly appliedthereto (cf. FIG. 12).

The material used for the plastic film 144 in this example is the samematerial as used for the plastic base 116. It is also possible, however,to use a different material which is suited for establishing a tightconnection with the material of the plastic base 116. This can be athermoplastic elastomer, for instance.

The adhesive film 142 serves as a bonding bridge between the plasticbase 116 and the first component 112.

Deviating from the illustrated configuration, the surface of theadhesive film 142 can also extend over the entire injection-moldedportion of the component 112 or project from the same, as a matter ofcourse. It is also possible to provide an appropriate adhesive film alsobetween the second component 114 and the plastic base 116.

The inflator 110 is manufactured as follows: To start with, the firstcomponent 112 (the inflator housing) as well as the second component 114(the igniter) are provided and the first component 112 is provided withthe adhesive film 124 in the later connecting area of the components(corresponding to the contacting area 140) by gluing one or moreappropriately cut pieces of the adhesive film 142 with the adhesivelayer 146 onto the corresponding positions of the first component 112,in this case on both sides in the area of the edge 122.

The adhesive of the adhesive layer 146 can be activated or hardenedalready now by the pressure during gluing. Alternatively, it isactivated or hardened by heating, which is effectuated e.g. duringinjection-molding by the heat influence of the liquid plastic material.

After the adhesive film 142 was glued onto the first component 112, thesecond component 114 is positioned relative to the first component 112,and both components 112, 114 are jointly surrounded by injection-moldedforming the plastic base 116, wherein both components 112, 114 areembedded at least partly in the plastic base 116.

During injection-molding the material of the plastic film 144 combineswith the injected plastic material by the fact that a surface layer ofthe plastic film 144 melts in a connecting zone 148 with the plasticbase 116. As an alternative, in the connecting zone 148 also a chemicalreaction can take place between the material of the plastic film 144 andthat of the plastic base 116, which reaction tightly and non-detachablyinterconnects the plastic film 144 and the plastic base.

The adhesive layer 146 forms a bonding bridge between the firstcomponent 112 and the plastic base 116, the bonding bridge beingresilient and/or plastically deformable so that tensions and shearforces occurring due to different thermal expansion coefficients of thedifferent materials are compensated. The adhesive layer 146 also acts asa packing between the first component 112 and the plastic base 116.

All described features can be combined with or exchanged for one anotherat the discretion of those skilled in the art.

The invention claimed is:
 1. An inflator (10) for a protective device ina vehicle, comprising: a housing; at least one igniter; and a base thatconnects the at least one igniter to the housing, wherein the base is atleast partially injection molded around the at least one igniter and thehousing to interconnect the base, the housing, and the at least oneigniter, the inflator further comprising a sealant applied in an areawhere the base abuts the housing.
 2. An inflator (10) according to claim1, wherein the abutting base and housing form at least part of the outerinflator surface.
 3. An inflator (10) according to claim 1, wherein thebase (32) is made of plastic.
 4. An inflator (10) according to claim 3,wherein the base (32) embeds portions of the at least one igniter (28),the at least one igniter (28) being pre-fabricated.
 5. An inflator (10)according to claim 3, wherein the base (32) forms an igniter plugreceipt (38).
 6. An inflator (10) according to claim 1, wherein thehousing is made of metal.
 7. An inflator (10) according to claim 6,wherein the base is injection-molded to the edge of an orifice (26) inthe housing in order to close the orifice (26).
 8. An inflator (10)according to claim 1, wherein the sealant (42) is applied to thetransitional edge of the abutting base and housing from outside theinflator (10).
 9. An inflator (10) according to claim 1, wherein thesealant (42) is introduced into a recess (54) provided at the transitionof the base and the housing.
 10. An inflator (10) according to claim 1,wherein in the application state the sealant (42) is liquid and/or is anacrylate adhesive.
 11. An inflator (10) according to claim 1, whereinthe sealant (42) can be applied in liquid state and can subsequently behardened by UV light.
 12. An inflator (10) according to claim 1, whereinthe sealant (42) features at least one of the following properties:Breaking strength according to ISO 527 [MPa] 2-4; Rupture elongationaccording to ISO 527 [%] 200-400; Viscosity at 23° C. according toBrookfield Sp/U and 3/100 [mPas] 400-800; Glass transition temperature(rheometer) [° C.] 10-30; Thermal expansion coefficient at 30-140° C.[ppm/K] 150-350; Density at 23° C. [g/cm³] 0.6-1.5; Water absorptionaccording to ISO 62, 24 h at 23° C. [%] 0.9-1.7.
 13. An inflator (10)according to claim 1, wherein the sealant (42) contains a fluorescentdye, and/or a dye deviating from the plastic material of the part towhich the sealant (42) is attached.
 14. A method for checking thedensity of an inflator (10) according to claim 13 by making use of acamera, wherein a sealing bead formed by the sealant (42) is irradiatedwith UV light to measure the density of the sealing bead.
 15. Aninflator (10) according to claim 1, further comprising an annular filter(76) disposed upstream of discharge orifices (78) which has two axialends, the filter being outwardly bent at one of its axial ends (80, 82).16. An inflator (10) according to claim 15, wherein the filter (76) hasthe same thickness in the bent portion as in a central portion which isadjacent to the bent portion.
 17. An inflator (10) according to claim15, wherein a filter wall, viewed in the axial cross-section, extendssubstantially in an S-shape between the ends.
 18. An inflator (10)according to claim 15, wherein the bent portion is adjacent to anupright edge (20) in a corner portion of the inflator (10) formed by acircumferential wall (16) and a bottom.
 19. An inflator (10) accordingto claim 15, wherein the filter (76) is positioned axially braced in theinflator (10) and/or is made of a wire mesh of wires havingsubstantially equal cross-sections.
 20. An inflator (10) according toclaim 15, wherein the filter (76) is laterally spaced apart from thedischarge orifices (78) provided in the housing (12) of the inflator(10).
 21. An inflator (10) according to claim 15, wherein the filter(76) is tapered toward an axial end (80, 82), opposed to the bent end.22. An inflator (10) according to claim 15, wherein the filter (76) isadjacent to inflator parts at its axial ends (80, 82) and the radiallyinnermost contacting position of the bent end is located radiallyfurther outward at the associated inflator part than the radiallyoutermost contacting position of the opposed axial end (80, 82) at theassociated inflator part.
 23. An inflator (10) according to claim 15,wherein the filter (76) is formed of wires having different thicknesses.24. An inflator (10) according to claim 23, wherein the filter (76) hasa tapered axial end (82) in the area of which the filter (76) has alarger length of thinner wires related to the volume than in theadjacent portion in the entire residual area.
 25. An inflator (10)according to claim 1, further comprising the at least one igniter (28)as a pre-fabricated component, and a combustion chamber (56) which isfilled at least partly with pyrotechnic material (58) adapted to beignited via at least one overflow orifice (66), characterized in that,after activating the at least one igniter (28) for igniting thepyrotechnic material (58), the overflow orifice (66) is movable relativeto the combustion chamber (56).
 26. An inflator (10) according to claim25, wherein the overflow orifice (66) is provided in a movable wall. 27.An inflator (10) according to claim 26, further comprising anintermediate chamber (62) receiving a boosting charge (64) which isadjacent to the at least one igniter (28) and which is separated fromthe combustion chamber (56) by a cap (60), wherein the cap (60) isprovided with the overflow orifice (66) and is arranged in the inflator(10) such that it is movable by activating the at least one igniter(28).
 28. An inflator (10) according to claim 27, wherein in thenon-activated state of the inflator (10) the cap (60) is adjacent at theend face to an elastic component (70), the component having a recess(72) into which the cap (60) projects.
 29. An inflator (10) according toclaim 28, wherein the elastic component (70) can be compressed by themovement of the cap (60).
 30. An inflator (10) according to claim 28,wherein the elastic component (70) is a filter made of mesh, and thatthe elastic component (70) is adjacent to the inside of an end face ofthe inflator (10).
 31. An inflator (10) according to claim 27, whereinthe cap (60) has at least one lateral overflow orifice (66).
 32. Aninflator (10) according to claim 25, wherein the cap (60) forms the onlypartition between the intermediate chamber (62) and a combustion chamber(56) at least partly filled with pyrotechnic material (58).
 33. Aninflator (10) according to claim 1, wherein the at least one igniter(28) is a pre-fabricated component, and further comprising anintermediate chamber (62) receiving a boosting charge (64) which isadjacent to the at least one igniter (28) and which is confined by a cap(60), wherein the cap (60) is pushed onto the base (32) with itsigniter-side open end.
 34. An inflator (10) according to claim 33,wherein the cap (60) is pressed with the base (32) or is placed onto thelatter while forming a press-fit.
 35. An inflator (10) according toclaim 33, wherein the cap (60) is attached to the base (32) such that itis movable by activating the at least one igniter (28).
 36. An inflator(10) according to claim 33, wherein the base (32) is formed byinjection-molding around the at least one igniter (28) and is providedfor fixing the at least one igniter (28) at the inflator (10).
 37. Aninflator (10) according to claim 1, wherein the housing (12) has acentral axis, and the at least one igniter (28) is embedded in the base(32), the housing (12) or a part connected to the housing (12) featuringa recess (34) into which the base (32) extends and portions of a wallforming the recess (34) being bent inwardly and an outwardly extendingbulge (48) being formed distant from the opening of the recess (34). 38.An inflator (10) according to claim 37, wherein the recess extends inring shape relative to the central axis.
 39. An inflator (10) accordingto claim 37, wherein adjacent to the recess the wall forming the recess(34) has the same wall thickness as in the bent portion.
 40. An inflator(10) according to claim 37, wherein, viewed axially, the recess (34) isS-shaped, wherein the opening portion of the wall forming the recess(34) extends outwardly.
 41. An inflator (10) according to claim 1,wherein the housing (12) has a central axis, and the at least oneigniter (28) is embedded in the base (32), wherein the housing (12) or apart connected to the housing (12) exhibits a recess (34) into which thebase (32) extends, and wherein a wall forming the recess (34) exhibits abottom portion (50) having an orifice (26) through which the base (32)extends, the bottom portion (50) having at least one projection (52)and/or a recess (54) at its opposed outsides in the area in which thebase (32) contacts the bottom portion (50).
 42. An inflator (10)according to claim 41, wherein the edge of the orifice (26) at anoutside has a convex projection, the projection (52) being formed by acircumferential bead.
 43. An inflator (10) according to claim 41,wherein the bottom portion (50) has an annularly circumferentialindentation (54) at the outside opposed to the projection (52) in thearea of the projection (52).
 44. An inflator (10) according to claim 41,wherein at each of the outsides at least one projection (52) and/or atleast one indentation (54) is formed in the area in which the base (32)contacts the same, wherein the at least one projection (52) and/or theat least one indentation (54) extend annularly around the orifice (26)and/or wherein the indentation (54) formed in the outside facing the atleast one igniter (28) is disposed radially inside the indentationformed at the opposed outside.
 45. An inflator (10) according to claim1, wherein the base (32) is formed by injection-molding around at leastportions of a wall forming an indentation (54) and/or is formed ofplastic material.
 46. An inflator (10) according to claim 1, wherein thehousing (12) has at its outer circumference a flange (24), wherein theflange (24) has an asymmetric shape so as to ensure a definite mountingposition at least in the twisting direction when fastening the inflator(10).
 47. An inflator (10) according to claim 46, wherein in the flange(24) at least one notch is provided as mounting positioning means (86).48. An inflator (10) according to claim 46, wherein plural notches areprovided which are disposed at different angular distances along theperiphery of the flange (24).
 49. An inflator (10) according to claim46, wherein as mounting positioning means (86) a positioning orifice isprovided in the flange (24).
 50. A module comprising an inflator (10)according to claim 46, wherein a holding element (92) is provided havinga counter piece engaging with a mounting positioning means (86) of theflange (24).
 51. A module according to claim 50, wherein the counterpiece includes at least one projection formed at the holding element(92).
 52. A module according to claim 50, wherein the holding element(92) has at least one fastening bolt (102), wherein the fastening bolt(102) contacts the outer periphery of the flange (24).
 53. A moduleaccording to claim 52, wherein the fastening bolt (102) does not contactthe flange (24) in the area of the mounting positioning means (86). 54.A module according to claim 50, wherein an airbag (96) is providedhaving an inlet orifice (98), wherein the edge of the inlet orifice (98)is clamped between the flange (24) and the holding element (92).
 55. Aninflator (10) according to claim 1, further comprising a combustionchamber (56) filled at least partly with pyrotechnic material (58) whichis confined by combustion chamber walls, wherein all combustion chamberwalls are made of the same metal.
 56. An inflator (10) according toclaim 55, wherein the combustion chamber walls are formed by pluralinterconnected parts, said parts being load-bearing parts.
 57. Aninflator (10) according to claim 55, wherein the combustion chamber (56)is an annular chamber.
 58. An inflator (10) according to claim 55,wherein the axial height of the inflator (10) is less than its diameter.59. An inflator (10) according to claim 1, further comprising acombustion chamber (56) disposed inside the housing (12) and containingpyrotechnic, gas generating material (58), the wall thickness of thecomponents of the housing (12) being 2.0 mm or less.
 60. An inflator(10) according to claim 59, wherein the housing comprises a diffuser(14) and a closing member (18).
 61. An inflator (10) according to claim60, wherein the diffuser (14) and the closing member (18) are fixed toeach other by a single connection defining the strength, the connectionbeing a circumferential weld (22) between the diffuser (14) and theclosing member (18).
 62. An inflator (10) according to claim 60, whereinthe wall thickness of the diffuser (14) is not more than 1.5 mm.
 63. Aninflator (10) according to claim 60, wherein the wall thickness of theclosing member (18) is not more than 1.9 mm.
 64. An inflator (10)according to claim 59, wherein upon activation a maximum pressure in thecombustion chamber of 300 bars is produced.
 65. An inflator (10)according to claim 1, wherein a combustion chamber (56) provided in theinflator (10) has a toroidal shape.
 66. An inflator (10) according toclaim 1, further comprising a combustion chamber (56) disposed insidethe housing (12) which contains pyrotechnic gas generating material(58), wherein the ratio of the maximum combustion chamber pressureoccurring upon activation of the inflator (10) to the wall thickness ofthe housing (12) is more than 150 bars/mm and less than 220 bars/mm. 67.An inflator (10) according to claim 1, further comprising pluraldischarge orifices (78) provided on the housing (12) and a combustionchamber (56) disposed inside the housing (12) containing pyrotechnic gasgenerating material (58), wherein the ratio of the entire discharge areaof the inflator (10) to the minimum and/or maximum wall thickness of thecomponents of the external housing (12) is more than 34 mm.
 68. Aninflator (10) according to claim 1, wherein the housing (12) has adiffuser (14) including a substantially cylindrical circumferential wall(16) and comprising a combustion chamber (56) disposed inside thehousing (12) and containing pyrotechnic gas generating material (58),wherein the ratio of the diameter of the diffuser (14) to the minimumwall thickness of the external housing (12) is between 35 and
 45. 69. Aninflator (10) according to claim 1, wherein the housing (12) has adiffuser (14) including a substantially cylindrical circumferential wall(16) and comprising a combustion chamber (56) disposed inside thehousing (12) and containing pyrotechnic gas generating material (58),wherein the ratio of the diameter of the diffuser (14) to the maximumaxial height of the inflator (10) is 1.8+0.1.
 70. An inflator (10)according to claim 1, wherein the housing (12) includes a flange (24) atits outer periphery, wherein the flange (24) is circumferential in aclosed manner and is planar and/or that the flange (24) is formed to befree of screwing orifices.
 71. An inflator (10) according to claim 1,wherein the housing (12) has a flange (24) at its outer periphery,wherein the flange (24) is circumferential and is planar, and/or thatthe flange (24) exhibits an annular clamping surface for an airbag (96)having a width ranging from 8 to 11% of the maximum diameter of thehousing (12).
 72. An inflator (10) for a protective device in a vehicleaccording to claim 1, wherein the housing (12) has a flange (24) at itsouter periphery, wherein the flange (24) is circumferential and planar,and/or in that the flange (24) exhibits an annular clamping surface foran airbag (96) having a width ranging from 5.5 to 7.5 mm.
 73. An airbagmodule (90) comprising an inflator (10) according to claim 1, the airbagmodule (90) further comprising a flange (24) at the outer periphery ofthe housing (12), an airbag (96) having an inlet orifice (98) defined byan orifice edge (100), and comprising a clamping element (104) opposedto the flange (24) for clamping the orifice edge (100) between itselfand the flange (24), wherein the orifice edge (100) is clamped by suchforce and the clamping surface is designed such that the lateraldisplacing force produced by a maximum pressure in the airbag (96) atthe orifice edge (100) is between 10 and 80% less than the frictionalforce generated by the clamping force between the orifice edge (100) andthe flange (24) and the clamping element (104).
 74. An airbag module(90) comprising an inflator (10) according to claim 1, the airbag module(90) further comprising a flange (24) at the outer periphery, an airbag(96) having an inlet orifice (98) defined by an orifice edge (100), andcomprising a clamping element (104) opposed to the flange (24) forclamping the orifice edge (100) between itself and the flange (24),wherein the clamped portion of the orifice edge (100) the inflator (10)has one or more recesses for circumferential positioning.
 75. Aninflator (10) according to claim 1, wherein the housing (12) has adiffuser (14) including a substantially cylindrical circumferential wall(16) including plural discharge orifices (78) and a closing member (18)which is welded with the diffuser (14), wherein the diffuser (14) andthe closing member (18) are in the form of a shell and wherein thedischarge orifices (78) are covered at the inside of the diffuser (14)by a tamping (84) in the form of a tamping film, and the tamping (84) isspaced apart from the inner edge of the closing member (18), a weld (22)being disposed between the diffuser (14) and the closing member (18).76. An inflator (10) according to claim 75, wherein the spacing betweenthe tamping (84) and the inner edge of the closing member (18) isbetween 3 and 5.5 mm.
 77. An inflator (10) according to claim 75,wherein the closing member (18) has a circumferential upright edge atwhich it is welded to the diffuser (14) and the smallest distance of theweld (22) from the tamping (84) is at least between 3 and 5.5 mm.
 78. Aninflator (10) according to claim 1, wherein the at least one igniter(28) has an igniter cap (36) containing a plastic material and is atleast partially surrounded by plastic injection molding, wherein thematerial of the igniter cap (36) and the material of the plasticinjection molding are selected such that the igniter cap (36) melts atleast partially with the plastic injection molding during injectionmolding.
 79. An inflator (10) according to claim 78, wherein the ignitercap (36) and the plastic injection molding consist of the same material.80. An inflator (10) according to claim 78, wherein the plastic materialcontains glass fibers.
 81. An inflator (10) according to claim 80,wherein the share of glass fibers is approximately 30% volume.
 82. Aninflator (10) according to claim 1, wherein the housing (12) and the atleast one igniter (28) are connected by means of the plastic injectionmolding.
 83. An inflator (10) according to claim 82, wherein the housing(12) has an orifice (26) and the plastic injection molding is molded tothe edge of the orifice (26) for closing the housing (12) to theoutside.
 84. An inflator (10) for a protective device in a vehicle,comprising: a housing; at least one igniter; and a base that connectsthe at least one igniter to the housing, the base including a portionover which an open end of a boosting charge-containing cap is positionedto attach the cap to the base, wherein the base is at least partiallyinjection molded around the at least one igniter and the housing tointerconnect the base, the housing, and the at least one igniter, theinflator further comprising a sealant applied in an area where the baseabuts the housing.